Herbert w



Patented Aug. 25, 1925.

UNITED STATES PATENT OFFICE.

HERBERT W. DAUDT, OF PENNS GROVE, NEW JERSEY, ASSIGNOR TO E. I. DU PONT DE NEMOURS &; COMPANY, OF WILMINGTON, DELAWARE. A CORPORATION OEDELA- WARE.

raoonss or MAKING nnnzorc' ACID.

No Drawing. Application filed June 2,

To aZZ whomit may concern:

Be it known that I, HERBERT W. DAUDT, .a citizen of the United States, and a resi-' dent of Penns Grove, in the'county of Salem :and State of New Jersey, have invented a certain new and useful Process of Making Benzoic Acid, of which the following is a specification. v

This invention relates to. a process of making benzoic acid and comprises heating a phthalic acid compound such as phthalic acid or a metal phthalate or preferably a mixture of phthalic acid and a metal phthalate, to a temperature 7 of between about 150 and 300 C. until the reaction is completed, or has progressed to the desired extent. 7

According to my invention benzoic acid is produced by either of the following pro cedures:

(0i) By heating airaqueous solution of phthalic acid; (b) By heating the aqueous solution of a neutral alkali-metal phthalate; or.

(0) By heating a solution containing both free phthalic acid and a phthalic acid salt of any of the following metals: 1.The alkali metals, including ammonium; I

2'.-The alkaline earth metals including magnesium;

ia-Copper, iron, nickel, cobalt, zinc, aluminum, and manganese, and probably others. I

The alkali-metals and the alkaline earth metals will be referred to generically as the alkali-forming metals. I

The --heating' of the phthalic. acid or, phthalate solution is referably carried out in an autoclave. emperatures between 150 and 300 C.'may be used,'but I prefer a temperature of from'about260 to 265C.

'The.mixt-ure which I prefer to use con tains equimolecular proportions of phthalic acid and sodium hydrogen phthalate, a mixture of this kind requiring about 20 hours at 260265 C. for the reaction to go to completion.

My process may be illustrated by the following example Run into an autoclave-500 lbs. of 8.4% sodium hydroxide (or 555 lbs. of 11.1% sodium carbonate solution). While agitatdesired extent.

1923. Serial no. 643,085.

ing, add 296 lbs. of 100% phthalic anhydride. (The phthalic anhydride may be the crude product obtained by.,the air oxidation process). Heat this mixtureat a temperatureof 260-265 C. for a period of 20 hours. After-cooling, dissolve the reaction product in a slight excess of sodium hydroxide. Filter ofl any insoluble matter. From the solution precipitate the benzoic'acid by 'addingsulphuric acid.[ This crude benzoic acid is then purified in the usual manner.

1. The process of producing benzoic acid. which comprises heating a, solution of a phthalic acid compound to a temperature between about 150 and 300 C. until formation of benzoic acid has progressed to the desired extent.

2. The process of producing benzoic acid- Which comprises heating a solution of a phthalic" acid compound to a temperature between about 260 and 265 C. until formation of benzoic acid has progressed to the The process of producing benzoic acid which comprises heating to a temperature of between 150 and 300 C.- a mixture containing phthalic acid and ametal salt of phthalic acid in the presence of water.

4. The process of producing benzoic acid which comprises heating to a temperature of between about 260 and265 C. a mixture containing phthalic acid and a metal salt of phthalic acid in the presence of water.

'5. The process-of producing benzoic acid which comprises heating to "ether a mixture of phthalic acid, water, an ate.

* 6. The process of producing benzoicacid which comprises heating together a mixture of phthalic acid, water, and an acid phthalate of an alkali forming metal to a temperature of from 150 to 300 C.

7. The process of producing benzoic acid which comprises heating together a mixture of phthalic acid, water, and an acid phthalate of an alkali-metal.

an acid phthal 8. The process of producing benzoic acid whigh comprises heating to a temperature between 150 and 300. C. a mixture containing water and about equimolecular pro ortions of phthalic acid and an acid pht alate of a metal.

9. A process as set forth in claim 8 in which the temperature is kept at from 260 to 265 C.

10. The process of producing benzoic acid which comprises heating to a temperature between 150 and 300 C. a mixture containing water, and substantial proportions of pht-halic' acid and an acid phthalate of an alkali-metal.

11. A process as set forth in claim 10 in which the temperature is kept at 260265 C.

12. The process of producing benzoic acid which comprises heating under pressure to a temperature between 150 and 300 C. a mixture containing phthalic acid, water, and the acid phthalate of an alkali-forming metal.

13. A process as set forth in claim 12 in which equimolecular proportions of the phthalic acid and the acid phthalate are used.

14. A process as set forth in claim 12 in which the reaction mass is heated to between 260 and 265 C. for about hours.

15. The process of producing benzoic acid which comprises-heating a mixture of Water, phthalic acid and an acid phthalate of an alkali-metal to a temperature of from 260 to 265 C. for about 20 hours, cooling and dissolving the reaction product in a slight excess of an alkali-metal hydroxide, filtering off any insoluble matter, and adding sulphuric acid to cause precipitation of the benzoic acid.

In testimony whereof I afiix my signature.

' HERBERT W. DAUDT. 

